Punch mounting, stripping and lubricating means for stamping presses



G. F. WALES 1,822,468

PUNCH MOUNTING, STRIPPING, AND LUBRICATING MEANS FOR STAMPING PRESSES Sept. 8, 1931.

med Sept. 20,

1928 2 Sheets-Sheet 1 (II I III II Sept. 8, 1931. c; w E 1,822,468

PUNCH MOUNTING, STRIPPING, AND LUBRICATING MEANS FOR STAMPING PRESSES V Filed Sept. 20, 1928 2 Sheets-Sheet 2 /0 I -?/4 I 5/4 I J Patented Sept. 8, 1931 PATENT OFFICE" UNITED STATES GEORGE F. WALES, 0F KENMORE, NEW YORK Application filed September 20, 1928. Serial No. 307,111.

This invention relates to a punch and spring mounting which is more particularly intended for use in connection with the punching and stripping mechanism of stamping or similar presses although the same may also be employed advantageously in other installations.

In the punching mechanism of stamping presses as heretofore constructed the punch has been so designed as to be difficult to fabr1- cate requiring more material and labor than is necessary. The punch has been held in position by means of a punch holder plate made to accommodate it, which plate has been rigidly fastened to the main shoe or holder by means of screws and dowel pins, the punch having a head larger than the body to prevent it from pulling out of the plate. 7 A

stripper plate has then been assembled around the punch and held in position by springs interposed between the stripper plate and the main shoe or holder to supply the force for stripping work from the punch, which springs have been placed under com pression by means of screws pro ect1ng through and suspended from the main holder, the screws also acting as guides to hold the stripper plate in place and under a continuous spring pressure. It has therefore been necessary to remove the entire umt from the press in order to replace a defective punch, because the stripper plate had to be removed first and then the punch holder plate had to be removed before the punch could be changed, a condition which has caused great expense and an inestimable loss of time in every plant using this type of tool. In an effort to eliminate the necessity for removing the punch holder plate when changing punches, certain so-called removable punches have been invented of which I am aware.

While these prior devices accomplish their purpose they are expensive to make and have the additional disadvantage that no provision has been made for removing the punch with the stripper plate still in place, nor for removing the stripper plate without tak ing the unit out of the press. It was therefore necessary to either remove the unit from the press in order to change a punch or else to provide a large enough hole in the strip per plate for the body of the punch to pass through, and in such cases the stripper does not therefore always surround the working part of the punch as closely as is necessary for producing good work.

A further disadvantage in the punching mechanisms heretofore used is that they necessitate fabrication of individual stripper plates for each punch holder unit and the method of making and assembling said stripper plates to the unit has also been unduly cumbersome and costly.

Another disadvantage of the punch stripping mechanism, as heretofore constructed, is that the amount of pressure exerted by the springs on the stripper plate has been unknown because in assembling the stripper plate with the unit, the determination of the quantity and size of springs to be used has been entirely a matter of guess work and resulted in experienced die makers putting in springs sufficient to produce a pressure much greater than was necessary, thus adding unnecessaryexpense in the making of the unit.

Another disadvantage of the punching mechanism heretofore known is that the same embodied no satisfactory way of lubricating the cutter portion of the punch. Heretofore this has usually been accomplished by applying the lubricant to the work with a swab or brush which has not only wasted lubricant and the time used to apply it but also has caused work produced to be smeared with the lubricant.

It is the object of this invention to provide a retaining device for rigidly holding a punch bit or end so that said bit can be made much more economically than the punches used at present; to make said retaining device so that the punch bit can be replaced quickly and conveniently without removing the punch holder plate; to provide a stripper unit which can be readily and conveniently assembled with and removed from the punching mechanism without disturbing any other part of the mechanism or causing it to be removed from the press; to provide a semifinished stripper unit so that the final operation of making the hole, through which the punch bit is to work,- can be done by the punch bit itself in the holder with which it is to function; to provide'a self contained stripping unit for punches in which a spring resistance of a predetermlned strength is built up as a unit so that the spring element is under an initial load when the same 1s as sembled with a retainin means, said load being of suflicient capacity to strip certain gauges of work from the punch andto be so calibrated; and to provide a stripping unit which will automatically lubricate the punch or punch bit.

In the accompanying drawings:--

Figure 1 is a fragmentary vertical section of a stamping press showing an approved form of removable punch and self-contained stripper unit embodying my invention in a retracted or inoperative position.

Figure 2 is a fragmentary vertical section of the same stamping press but showing the same in operation.

Figure 3 is an enlarged fragmentary vertical section of the locking means for holding the punch sleeve and stripping unit assembled with the punch guide stem.

Figure 4 is an enlarged fragmentary view of the lower end of the punch guide stem showing a detail of the seat for the locking wed e.

Fi gure 5 is a view of the punch, punch sleeve, and locking wedge element as this unit ap ears when removed from the press.

igure 6 is a fragmentary horizontal section taken on line 6-6 Fig. 8.

Figure 7 is a view of the wedging locking element showing a means for preventing separation of this element from the sleeve.

Figure 8 is a fragmentary vertical section of a conventional type of stamping press punch showing how the same may be fabricated so as to accommodate my stripper unit.

Fi re 9 is a plan view of an approved type of In ricating retainer as used in my stripper unit when said unit is used to lubricate the punch.

Figure 10 is a fragmentary vertical section of a stamping press punch showing attached thereto a form of stripping unit embodying the lubricating feature of my invention.

Figure 11 is a vertical section of an approved type of stripper unit as provided'in a semi-finished state so that the hole through which the punch is to work can be made by the punch itself.

Figure 12 is a vertical section of an approved form of locking device for my removable punch and sleeve when the same is used without the stripper unit.

Figure 13 is a section taken on line 13-13 Fig. 12 in the direction of the arrows.

Figure 1d is an enlarged fragmentary section of the wedging means for locking the punch sleeve to the guide stem.

Figure 15 is a plan View of the locking or shifting ring.

In the following description the reference characters indicate like parts in the several figures of the drawings.

Although this invention is capable of use in various installations the same is shown in the present case in the drawings as used in connection with the punching and stripping mechanism of a stamping press of the kind commonly used for blanking, piercing, trimming, punching and notchin sheet metal. It is obvious that the stripping unit described in the drawings may be used with various types of punches and stripping mechanisms and that the punch guide, sleeve, and bit construction may be used with other types of strippers and mechanisms.

The numeral 10 represents the punch holder or body of the means whereby the punch is supported upon the vertically movable slide or carrier of the press in which my invention is embodied, and 32 represents the die holder or body which is adapted to be mounted on the stationary bed of the press and upon which is supported the die which cooperates with the punch on the slide or carrier.

To the underside of the punch holder is detachably secured the punch shoe 11 whereby the punch is detachably mounted on the punch holder, the connection between this shoe and the holder being preferably effected by means of a screw 111 which passes through the shoe from the underside thereof into the underside of the holder, as shown in Figs. 1, 2, 8 and 10.

The punch in the present case is preferably constructed in the form of a short bit 16 which is provided at its upper end with a head 116 preferably of conical form and its lower end co-operates with the opening 131 of a die 31 which is detachably secured to the upper side of the die holder by means of a screw 231 passing through this die from the upper side thereof into the holder below the same, as shown in Figs. 1, 2, 8 and 10.

Although various means may be provided for detachably mounting the punch or bit 16 on the shoe 11, those shown in the drawings are preferred and comprise an abutment having a cylindrical reduced stem 12 which is engaged at its lower end 27 by the upper headed end of the punch or bit 16 and provided at its upper end with a cylindrical enlargement or head 13 which is interposed between the underside of the punch holder or body 10, and an upwardly facing shoulder 14 formed in the upper enlarged part 111- of a vertical opening in the punch shoe, the lower reduced part 28 of this opening receiving the reduced part 12 of this punch abutment or supporting stem, and a centering and supporting sleeve 15 surrounding the opposing parts of the punch 16 and the stem 12, and having its upper part arranged in the reduced portion 28 of the opening in the shoe, but terminating short 0 the under side of the head 13, as shown at 34, and also provided adjacent to its lower end with an internal upwardly facing shoulder 115 which bears against the underside of the head 116 on the punch or bit 16. The punch or bit may be held in this working position on the punch shoe by any suitable means, but preferably by means which are associated with a stripper unit whereby a sheet of metal 30 after having been perforated by cooperation of the punch and die will serve to strip the sheet of metal from the punch preparatory to performing the next operation.

This stripper unit may be constructed in various ways, that shown in Figs. 1-7 being organized as follows The numeral 19 represents an inner sup porting sleeve adapted to engage frictionally with the lower cylindrical part of the centering sleeve 15 and provided in its bottom with an opening 119 through which the adjacent part of the punch passes, as shown in Figs. 1 and 2.

At its upper end this supporting sleeve is provided with a laterally projecting external flange 24. Surrounding the inner supporting sleeve is an outer bearing sleeve 18 which is spaced from the inner sleeve 19 so as to form an annular space therebetween. This outer sleeve is provided at its upper end with an internal annular flange 36 which is adapted to bear against the upper side of the external flange 24 on the inner sleeve. At its lower end the outer sleeve 18 is provided with a head having a central perforation 118 for the passage of the punch 16"and also forming an internal flange 25.

Arranged in the annular space between the inner supporting sleeve 19 and the outer bearing sleeve 18 is a helical spring 17which bears at its upper end against the underside of the external flange 24 while its lower end bears against the upper side of the internal flange 25 of the outer sleeve, as shown for example in Figs. 1 and 2. This spring resistance unit can he slipped onto or off from i the lower end of the bit 16 and the centering sleeve 15 without disturbing any other partsof the press. The means for locking the centering sleeve 15 on the abtument stem 12 and thereby holding the punch in place against the underside of this stem, preferably comprises a transversely movable locking member 20 having the form of a pin which is guided in an opening 120 in the side of the centering sleeve 15 and having an inclined inner end 112 andan inclined outer end 123 which inclined ends on surfaces converge downwardly; The inner inclined face 112 is adapted to engage with thecorrespondingly inclined face 22 formed on the bottom of a notch on the adjacent side of the abutment 12, and the inclined outer end 123 of this locking member is ada ted to be engaged with the corresponding y inclined face 23 formed on the upper portion of the bore of the inner supporting sleeve 19.

Although the locking member 20 is free to move laterally or radially on the centering sleeve 15, the extent of this movement is limited so as to prevent complete displacement of the locking member 20 from the centering sleeve 15 by means of a retaining pin or key 21 which passes vertically through this locking member, and is arranged within an upright opening or passage 29 extending up wardly through the centering sleeve 15 from the lower end thereof and intersecting the guide way 120, said retaining pin also being of sufficient length that the rotary motion of the locking member 20 will be limited by engagement of one end or the other of the pin 21 with the sides of the opening 29, and thereby retain the locking block 20 in position for properly engaging its inclined faces 112, 123 with the inclined faces 22 and 23 of the abutment stem 12 and the inner supporting sleeve 19.

In assembling the stripper unit with the punch and its support, the inner sleeve 19 is pushcd upwardly upon the lower end of the centering sleeve 15" with the parts in such position that the incline 23 of the supporting sleeve 19 will engage with the outer inclined face 123 of the locking member 20, whereby the latter is pushed inwardly and caused to engage its inclined inner end 112 with the inclined face 22 of the abutment stem 12. When the parts are in this position the punch orbit is positively interlocked with the abutment member 12 through the medium of the centering sleeve 15, and after the abutment member has its head 13 secured bet-ween the opposing surfaces of the punch holder 10 and the punch shoe 11, it follows that after the punch has descended and perforated the sheet of metal, this punch will be compelled to withdraw therefrom as the holder of the punch rises with the carrier or slide of the press.

In the normal position of the parts, when the punch is retract-ed or in its inoperative position, the lower end or face of the outer bearing sleeve 18 is either flush with or slightly below the lower end of the punch so that this lower end of the outer sleeve 18 will rest upon the sheet of metal which is being punched and held against further downward movement, whereby the stripping spring 17 will be compresse between the inner supporting sleeve of the stripping unit and the outer bearing sleeve 18 thereof, as the punch completes its operative stroke. After the punch is lifted on its return stroke the resilience of the spring 17 holds the outer bearing sleeve firmly against the upper side of the sheet of metal which has been operated upon and prevents the same from following the punch or bit, whereby the sheet of metal 1s 5 stripped or disenga ed from the bit or punch leavin the latter ree to perform the next operation.

During the downward motion of the bit with the stripper unit mounted thereon, the upward pressure which is exerted against the inner supporting sleeve through the medium of the spring 17 will cause this inner sleeve to be pressed upwardly with gradually increasing pressure as the punch descends, whereby the locking member 20 wlllbe pressed radially inward with reference to the abutment member 15 and thereby increase the interlocking effect of the means whereby the punch is held on the sleeve 15 so that the 20 punch can not become loose on its support during the punching operation, but instead is held thereon with greater firmness.

The stripping spring 17 is put under an initial load before the same is placed between the inner and outer sleeves 19, 18 of the stripper and when these sleeves are interlocked to limit the longitudinal separation of the same, this initial load in the spring is always maintained and never reduced, but

this load is increased whenever the outer sleeve 18 engages the work piece to be stamped and is held stationary thereby, because at this time the inner sleeve 19 is moved downwardly and increases the compression of the spring 17 whereby the ejecting effect of the stripping unit is increased.

In order to prevent the lower end of the inner supporting sleeve 19 from exhausting its wedge or cam action against the locking member 20 for holding the punch firmly in place, this sleeve is made sufficiently long so that when the same is pressed upwardly by engagement of the outer bearing sleeve 18 with the top of the sheet of metal, there will still remain a gap or clearance space between the lower end of the centering sleeve 15 and the bottom 119 of the inner bearing sleeve, as clearly shown at 26 in Figs. 1 and 2.

If at any time it is desired to increase or decrease the stripping efiect of the respective stripper unit this can be readily accomplished by pullin off the respective stripper unit which is t en in use and replacing the same by another having either a stronger or weak- 6 er spring, as best suits the character of the work in hand, and this means also permits of replacing a stripper unit in which the spring has been broken by another stripper unit having a new spring.

When it is desired to remove the bit or punch itself this can be readily accomplished by first removing the stripper unit therefrom, thus releasing the locking member or pin 20 from engagement with the inclined recess 22 on the side of the abutment 12, then pulling the sleeve 15 downwardly out of the reduced part 28 of the punch shoe opening and then taking the punch or pin 16 out of the sleeve 15 If desired, the shoe 11 with the parts mounted thereon may be taken out together after removing the fastening screws 111, and it is also possible to take out the entire punch mechanism and the stripper unit associated therewith together with the punch holder 10 at the same time by simply removing-this punch holder from the carrier or slide of the press.

It will be noted that during the punching operation the punch or bit 16 is provided with a solid support in view of the fact thatthe upper end of the punch engages with the lower end of the abutment 12 and the latter engages directly with the holder 10 so that there is no slack during the actuation of the punch.

If desired, the head at the lower end of the outer bearing sleeve 18 may be left solid or imperforate, as shown at 43 in Fig. 11, which permits the lower end of the punch, during the first time the same performs a punching operation, to form its own hole in the lower head of this outer bearing sleeve, and thereby enable a tighter fit to be obtained between the punch and the bottom of the out er bearing sleeve 18 than would otherwise be possible, this being particularly important when the punch is of irregular form in crosssection, and considerable difliculty and expense would be involved in providing an opening in the lower head of the bearing sleeve 18 of the stripper unit in order to secure a good fit between the same and an irregularly shaped punch.

Instead of employing a locking mechanism between the centering sleeve 15 and the abutment stem 12 for the purpose of holding the bit 16 against the stem, such locking mechanism may be omitted, as shown in Fig. 10. In the last mentioned construction the retention of the centering sleeve 15 on the abut ment stem 12 in the opening 28 of the punch shoe 11 is effected by a set screw 128 and the engagement of the inner supporting sleeve 19 of the stripper unit with the centering sleeve is eflected solely by friction. The set screw 128 works in a threaded opening in the shoe 11 and is provided at its inner end with a conical surface 228 which engages with the upper part of a conical recess 215 in the side of the sleeve 15 so that upon tightening the screw 128 the latter will exert a wedge action on the sleeve 15 and draw the same upwardly so that the punch 16 and abutment 12 are held tightly together, and the head 13 of the abutment is retained against the holder 10.

If desired a locking mechanism may be employed between the centering sleeve 15 and the abutment stem without using a stripper mechanism, as shown in Figs. 12, 13, 14 and 15.

In this construction a locking member 47 is employed which moves transversely in a guide opening 147 in the side of the centering sleeve 15 and engages with the inclined bottom 22 of a notch in the adjacent partof the abutment stem 12, and this locking member or pin 47 may be either tightened in its working position or released for the purpose of permitting removal of the sleeve 15 from the stem 12 by means of a rotary cam sleeve 48 turning circumferentially on the periphery of the centering sleeve 15, and provided with an eccentric face 49 which is adapted'to engage with the outer end 149 of the locking member 47, as shown in Figs. 12, 13 and 14. This eccentric face 49' is preferably made in the form of a groove which is semi-circular in cross section, as shown in Fig. 12, so as to provide a large bearing surface on this wedge or cam surface for engagement with the locking member 47, and thereby reliably hold the latter in engagement with the abutment stem 12.

Instead of making the bit and abutment member in separate parts, the same may be constructed integrally, as shown'at 116 and 40 in Fig. 8, in which case the centering sleeve is dispensed with and the upper end of the shank 140 of the bit is provided with an enlarged head 214 which engages with the correspondingly shaped rabbet 314 at the upper end of an opening in the punch shoe 11 while the reduced part 140 of the bit immediately below its head 214 engages with the reduced part 141 of said opening. In this case the bottom of the supporting sleeve 219 bears d1- rectly against a downwardly facing shoulder on the bit, as shown at 216 in Fig. 8, and this inner supportin sleeve is detachably mounted on the bit by means of a spring tongue 41 which is stamped out of the body of this sleeve and projects inwardly therefrom into engagement with an annular groove 42 on the periphery. of the central part or shank 140 of the bit 116, as shown 1n Fi 8.

In order to lubricate the bit and enable it to work more efficiently during the punching operation, means are provided for applying a film of lubricant thereon as the same moves downwardly out of the stripper unit. For this purpose the space within the stripper unit between the inner and outer sleeves thereof is filled with a lubricant such as oil which surrounds the lower part of the bit which is exposed within this chamber. As the bit passes through the bottom opening in the outer bearing sleeve 18 only a thin film of lubricant is left thereon, inasmuch as any excess is scraped therefrom and retained within the stripper unit, thereby economizing in the use of a lubricant.

Inasmuch as the bit or punch gradually becomes shorter due to wear and repeated sharpening at its lower end, the working face at the lower end of the same would intime be arranged above the inner side of the bottom of the bearing sleeve 18 of the strip r unit, and thereby permit the lubricant within the reservoir or supply chamber between the stripper sleeves to escape and become wasted. To avoid this, a lubricant retaining disk is employed which is preferably constructed in the form of an upwardly dished disk 44 which rests with its lower marginal part on the bottom of the bearing sleeve 18 and is held in place thereon by means of the stripper spring 17 engaging therewith, while the elevated central part of this retaining disk is provided with a central opening 45 through which the lower part of the punch passes. In this case, however, an additional opening 46 is also formed in the bottom of the outer disk 18 for the passage of the punch, as shown in Fig. 10.

In this construction the lubricant within the stripper sleeves is held away from the bottom of the outer sleeve 18 and at such a. distance that at no time will the lower end of the bit pass above the disk 44, thereby preventing leakage and waste of lubricant.

When required, the reservoiror space between the inner and outer sleeves 19 and 18 may be replenished from time to time throu h an opening 37 in the outer sleeve 18 near t a top thereof, as shown in Fig. 10.

In the construction of the stripper mechanism of stamping presses as heretofore constructed, the breaking of a punch or the replacement of a punch when necessary required a very considerable dismantling or dismemberment of the press in order to remove the parts of the stripper mechanism and gain access to the punch itself, which operation, together with an equally diflicult and laborious operation of replacing the punch and the stripper mechanism, involved a considerable waste of time and unnecessary expense. Such removal and replacement of the stripper mechanism is also frequently necessary when the particular character of the work in hand requires the springs then in use to be changed for others of a lighter or heavier capacity in order to enable the press to operate in the most satisfactory man'- ner.

This removal and replacement of the punch and the stripper mechanism is one of the most difiicult tasks which is experienced in the making of dies and punches for presses inasmuch as the dies and punches, during the making of the same, must be frequently mountedand unmounted in order to check the progress of the work and make required changes, and this therefore involves considerable expense and labor according to the methods heretofore in common use.

All of the above disadvantages in the making of the dies and punches and in the operation of the same, are practically eliminated and at least minimized by mounting the punch and the stripper mechanism in accordance with this invention. Although the various forms shown in the drawings represent a practical embodiment of my invention it is to be understood that the same may be varied as to details and still contain the essence of my improvements as summed up 1n the following claims v I claim as my invention 1. A stamping press comprising a punch holder, a punch shoe detachably connected with said holder and provided with an open" ing having a narrow lower part and an enlarged upper part, a punch abutment having a lower narrow stem arranged in the lower narrow part of said opening and an upper enlarged head arranged between the enlarged upper plant of said openin and said holder, a punc having a head an engaging the lower end of said stem, a centering sleeve which receives the adjacent end portions of said abutment and punch and which has its upper part arranged in the narrow part of said opening and provided in its lower part with an upwardly facing shoulder engaging the underside of said head on the punch and a spring resistance arranged adjacent to said punch and adapted to bear yieldingly agamst the work-piece and strip the latter from the unch.

p 2. A stamping press com rising a punch holder, a punch, and means "or mounting the punch on said holder including a shoe detachably connected with the holder, an abutment mounted on the shoe and held against downward movement thereon, a centering member arranged between the abutment and shoe and embracing said abutment and punch, means for detachably connecting the punch and centering member, and a spring resistance arranged adjacent to said punch and adapted to bear yieldingly against the wort.- piece and strip the latter from the punch.

3. ll. stamping press comprising a punch holder, a punch and means tor mounting the punch on said holder including a shoe detachably connected with the holder, an abutment mounted on the shoe and held against downward movement thereon, a centering member arranged between the abutment and shoe and embracing said abutment and punch, means -for detachably connecting the punch and centering member including a laterally movable locking member guided on said centering member and engageable with a notch in said abutment and a spring resistance arranged adjacent to said punch and adapted to bear yieldingly against the work-piece and strip the latter from the punch.

a A. stamping press comprising a punch holder, a punch and means for mounting the punch on said holder including a shoe detachably connected with the holder, an abutment mounted on the shoe and held against ,gagin assesses downward movement thereon, a centerin member arran ed between the abutment and shoe and em racing said abutment and punch, means for detachably connecting the punch and centerin member includin a letorally movable loc ing member gui ed on said centering member and engageable with a notch in said abutment, and a retaining pin projecting from said lockin member and arranged in a recess formed 111 said centerin member and a spring resistance arranged a jacent to said punch and adapted to bear yleldingly against the workpiece and strip the latter from the punch.

5. A stamping press comprising a punch holder, a punch and means for mounting the punch on said holder including a shoe detachably connected with the holder, an abutment mounted on the shoe and held against downward movement thereon, a centering member arranged between the abutment and shoe and embracing said abutment and punch, means for detachably connecting the punch and centering member, including a laterally movable locking member guided on said centering member and having a wedge face eng)with a corres ondingly shaped face on said a utment mem r and a spring resistance arranged adjacent to said punch and adapted to bear yieldingly against the workpiece and strip the latter from the punch.

6. .A stamping press comprising a punch holder, a punch and-means tor mounting the punch on said holder including a shoe dee tachably connected with the holder, an abut-' ment mounted on the shoe and held against downward movement thereon, a centering member arranged between the abutment and shoe and embracing said abutment and punch,

means for detachably connecting the punch and centering member including a laterally movable loclring member guided von said centering member and engageable with a notch in said abutment and a tubular member surrounding the centering member and having a wedge face engaging with the outer end ct said locking member and a spring resistance arranged a jacent to said punch and adapted to bear yieldingly against the work-piece and strip the latter from the punch.

7 A stamping press comprising a relatively movable punch holder and die holder, an abutment detachably mounted on the punch holder, a punch engaging said abutment, a centering sleeve embracing said abutment and punch, and a stripper unit mounted on said centering sleeve.

8. A stamping press comprisin a relatively movable punch holder and die holder, an abutment detachably mounted on the punch holder, a punch engaging said abutment, a centering sleeve embracing said abut ment and punch. and a stripper unit comprising an inner supporting sleeve mounted on the centering sleeve and having an external flange, an; outerjhearmg sleevef-having an internal flange, a pin arranged in vsaid centering sleeve; and engaged with said abutment f and innersl posed betweeii'said flanges:

9 A stamping. press comprisin azrelatively movable punclrholder and d e holder,

an abutmentfletacjha 'bly mounted "on the punch holder, a p'unch engaging said abutment, a centering sleev'embracing said abutment and;punch, and ai'st'ripper unit compris} ing a spring under initial load,"and retaining: means mounted on said centering means for preventmg" reduction in the initial load-of said spring but permitting increase in said lead, including an inner supporting sleeve mounted on saidflcenteringmember andihaving an upper external flange, an outer bearing sleeve surrounding the supporting sleeve f. and having anupper internal ange adapted o engage :the upper; side of the external flange on x-said inner sleeve and also having a lower internal flange, and a spring inter- :posed between the external flange of said inner sleeve and the'lower internal flange of said outer; sleeve.

' 10. A;s'tamping press comprisin a relatively movable punch holder and die holder,

an abutment detachably mounted on the punch holder, a punch engaging said abutment, a centering sleeve embracing said abutment and punch, and a stripper unit comprising a spring under initial load, retaining means mounted on said centering means for preventing reduction in the initial load of said spring but permitting increase in said load, including an inner supporting sleeve mounted on said centering member and having an upper external flange, an outer bearin sleeve surroundin the supportin sleeve g g g i and having an upper internal flange adapted to engage the upper side of the external flange on said inner sleeve and also having a lower internal flange, and a spring interposed between the external flange of said inner sleeve and the lower internal flange of said outer sleeve, and means for coupling said abutment, centering member and stripper unit including a locking member slidable transversely on the centering member and provided at its inner and outer ends with inclined faces which converge downwardly and engage with correspondingly inclined faceson the abutment and inner supporting sleeve.

In testimony whereof I, hereby aflix my signature.

GEORGE F. WALES.

eeve', anda resistance spring inter- 

